This invention relates to radially fed microwave signal combiner/distributor apparatus and more especially but not exclusively, it relates to such apparatus for use in microwave amplifier arrangements for radar systems or other microwave systems.
Known radially fed signal combiner/distributor apparatus comprises a central microwave signal connector which is coupled via radially extending paths to several equiangularly spaced, circumferentially disposed microwave signal connectors surrounding the central connector, whereby microwave energy can be fed either to the central connector for distribution to the circumferential connectors or alternatively it can be fed to the circumferential connectors and combined at the central connector.
In order to fabricate an amplifier arrangement for the high power amplification of microwave energy it is known to use two such signal combiner/distributors, as described in an article by Mr B J Sanders entitled "Radial Combiner Runs Circles Around Hybrids" in `Microwaves` November 1980, pp. 55-58 the respective circumferential connectors of which are mutually coupled by a number of individual low power amplifiers so that the central connector of one of the two signal combiner/distributor serves as an input connector via which signals are fed radially to the amplifiers, and so that the central connector of the other of the two signal combiner/distributors serves as a high power output terminal fed radially from the amplifiers.
This known amplifier arrangement thus uses a number of low power amplifiers to provide for high power amplification and such an arrangement may therefore be used to replace a travelling wave tube or a klystron transmitter.
In known signal combiner/distributor arrangements, the circumferential connectors are each connected to a balun loop coupler which serves to facilitate the transmission or reception of microwave energy radially. Thus, in signal combiner/distributor apparatus for use in microwave amplifiers which comprise a great many circumferential connectors, a correspondingly large number of balun loop couplers are required which are costly to manufacture and time consuming to assemble.
Moreover, in the known apparatus, in order to suppress higher order modes which arise from within the structure and/or from variations in termination impedances, resistors are connected within the apparatus between the balun loops, and if a resistor should fail the apparatus must be dismantled in order to replace it.
It is an object of the present invention to provide radially fed signal combiner/distributor apparatus which is relatively inexpensive to produce, simple to construct and reliable in operation.